Thread:Sweetangel823/@comment-25708364-20170823010032/@comment-17703532-20170824052018

Mō iya and Mou iya are the same; The line above the o indicates a long vowel, which is in romaji spelled as "ou" or "oo" (with "ou" being the more common). It's basically a less formal way of saying "mou iya da" (which, in a sense, is a less formal way of saying "Mou iya desu")